Aircraft: A321
Phase of flight: Climb; Initial Climb
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy

The aircraft in question was operating with MEL 27-XXX open; Spoilers #2 or #4. After engine start on both legs; an ECAM message was received regarding the spoilers but this was disregarded as a result of the MEL. Upon further reflection; these messages should have triggered further investigation on my part; as the presence of such an alert was not mentioned in the MEL. However; I had noted a write-up in the MEL about spurious messages - made by a Check Airman - which was subsequently signed off by Maintenance as essentially being unimportant. The aircraft had flown 4 legs the day prior with the MEL active. Also; at the time of this incident; I had approximately 100 hours of experience in any Airbus aircraft.The first leg of the day was flown uneventfully. Immediately after takeoff on our second leg of the day with the same plane; an ECAM caution and audio alert was triggered for a F/CTL SPLR FAULT. The message subsequently cleared itself; but then a few seconds later; would trigger again. This cycle repeated itself approximately every 20-30 seconds for about 20 minutes; until the flight reached FL270; where the message stopped cycling and instead remained. Initially; after exiting the sterile period; ACARS messages were sent and a brief exchange ensued. An emergency return to ZZZ was offered as an option; but given that we were well above maximum landing weight and the ECAM did not require us to land as soon as possible; I elected to continue the climb.Upon reaching cruise altitude; I transferred the flying duties to the FO (First Officer) and verbally contacted Dispatch and eventually Maintenance Control. Maintenance had no inflight suggestions and stated that they would look at it when the plane is on the ground. At this point; the Dispatcher and I discussed our options. Since the ECAM mentioned FUEL CONSUMPTION INCREASED and FMS PRED UNRELIABLE and we still had just under 3 hours to go on a flight planned to land with just 8;000 LBS of fuel; the decision was made to divert to ZZZ1. Dispatch changed our destination and we proceeded to an uneventful landing in ZZZ1. An emergency was not declared. While on the ground in ZZZ1; one of the responding mechanics reported to me that he discovered that the MEL procedures were not properly complied with when the item was deferred and that Spoiler Pair #2 was inadvertently deactivated instead of Pair #4. Apparently; the aircraft had flown 4 legs in this condition prior to our operating it. He mentioned to me his concern that on the [day prior]; a previous crew; the previously mentioned Check Airman had also apparently experienced a similar condition; wrote it in the logbook; only to have Maintenance simply clear the entry by writing 'info noted.' He expected that the aircraft would be taken out of service to fix the underlying issue. However; the decision was made to clear the write-up that I made and allow the deferral to continue. Based on the information that was relayed to me by this Mechanic; it appears that the initial error of deactivating the wrong spoiler pair was attempting to be covered up. This is very concerning.My relative inexperience with Airbus aircraft allowed me to be lulled into a false sense of security when it came to ECAM messages that appeared to relate to the MEL item. Seeing a write-up about spurious messages being handled the way it had been also led me to believe that there was nothing out of the ordinary; when realistically; there was a major error made by a certificated Mechanic. In retrospect; what was displayed on the F/CTL page should have alerted me to a problem; with both Spoiler Pairs #2 and #4; but I assumed that this was the same display that the mechanics and all of the other pilots who operated the aircraft before me also saw. The MEL does not give us specific guidance as to what should be displayed on this page with the MEL active; but I presume that the AMM (Aircraft Maintenance Manual) procedure referenced should tell the Mechanic whatshould have been displayed.More information in the MEL document detailing what exactly should be displayed on the SD (System Display) and what messages the crew should or shouldn't expect for a given MEL. Also; if there was indeed an attempt to cover up a maintenance error; I think this case should be used as an example as to how to properly correct an error. After takeoff we got an ECAM for flight spoiler fault that was reoccurring. We had this aircraft on the previous leg and got the ECAM and cleared it but this one kept returning. We still thought it was associated with the MEL on the Aircraft Spoiler Surface 4 INOP but Spoiler Surface 2 was also INOP. The Captain had reviewed the logbook before the previous flight and seen another crew had this happen and Maintenance had signed off [that] it was normal for the MEL. The Captain got in touch [with] Maintenance through Dispatch and they wanted us to divert to ZZZ1. We diverted and landed uneventfully.I think Maintenance improperly deferred the Spoiler Surface 4 and after a crew wrote it up; did not verify it was correct. The MEL should have had us view the Flight Control page instead of the HYD SD page for amber information of #4 Spoiler ONLY amber or #2 Spoiler ONLY. A321 flight crew reported ECAM messages appearing and experiencing flight degradation due to Maintenance performing improper procedures around an MEL and inactivating the wrong spoiler pair.